a. Technical Field
The instant disclosure relates generally to power electronics systems, and more particularly to a gate driver circuit for power conversion apparatus.
b. Background
This background description is set forth below for the purpose of providing context only. Therefore, any aspects of this background description, to the extent that it does not otherwise qualify as prior art, is neither expressly nor impliedly admitted as prior art against the instant disclosure.
In a power electronics circuit, a so-called gate driver circuit is important and challenging to design because of the electrical stress incurred by the subject switching device being controlled by the driver circuit during the switching process. For example, an electrical voltage stress affects the subject switching device during the switching off process while an electrical current stress takes place during the switching on process. In some applications, a different switching speed for switching ON versus switching OFF may be desired and/or implemented. In particular, switching speed usually determines the switching loss. The faster the switching speed, the lower the switching loss thereby the higher the switching frequency. On the other hand, that means at the same loss level, the faster-switching-speed semiconductor yields to higher switching frequency, which results in the smaller passive components thereby a higher power density. For the conventional Si IGBTs, for example, the switching speed may be about >100 nanoseconds (ns) to turn on/off, while for a GaN device, such value may drops to ˜10 ns, which means the switching loss is ˜1/10 of the conventional Si devices. This will yield to much higher efficiency or 10 times higher power density.
The mechanism implemented by the gate driver circuit involves charging and discharging the input capacitance Ciss of the switching device being controlled. In theory, different switching speeds and turn-on/turn-off times means different impedances of a gate-drive loop.
In addition, wide-bandgap (WBG) devices, such as Silicon Carbide (SiC) and Gallium Nitride (GaN) devices are becoming more popular due to their higher switching frequency capability, lower switching loss and higher thermal capability as compared to conventional silicon (Si) devices. In the case of an enhancement-mode GaN HEMT, it may be appreciated that the parasitic capacitance is much smaller than for traditional silicon devices (e.g., ˜pF level). This reduced level allows faster switching speed; however, this characteristic also requires increased care to control and reduce the gate-drive loop inductance in order to minimize undesirable side effects, such as induced ringing of the gate voltage.
Accordingly, there is therefore a need to overcome one or more of the problems in the art.
The foregoing discussion is intended only to illustrate the present field and should not be taken as a disavowal of claim scope.